Sea level and global ice volumes from the Last Glacial Maximum to the Holocene

Abstract

The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in <2,000 y at the onset of the glacial maximum ∼30,000 y before present (30 ka BP); (ii) a slow fall to -134 m from 29 to 21 ka BP with a maximum grounded ice volume of ∼52 × 10(6) km(3) greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka(-1) punctuated by periods of greater, particularly at 14.5-14.0 ka BP at ≥40 mm⋅y(-1) (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100-150 y ago, with no evidence of oscillations exceeding ∼15-20 cm in time intervals ≥200 y from 6 to 0.15 ka BP.

Keywords: Holocene; Last Glacial Maximum; ice volumes; sea level.

Fig. 1.

Distribution of far-field sea-level data for the past 35 ka. (A) Depth−age relationship of all data with 2σ error estimates. (B) Time distribution of the data. (C) Geographic distribution of all far-field coral (red dot) and sediment (black triangles) data.

Fig. 2.

Minimum variance function ${\Psi }_k^2$ [4] as function of (A) lithospheric thickness H, (B) upper-mantle viscosity η_um, and (C) lower-mantle viscosity η_lm across E space defined by [5] with η_lm/η_um ≤ 500. Unique solutions are found for H and η_um but two minima are identified for η_lm: a low lower-mantle viscosity solution at η_lm ∼2 × 10²¹ Pa s (red dot) and a high lower-mantle viscosity solution at η_lm ∼10²³ Pa s (blue dot). The corresponding 95% confidence limits ${\Phi }_k^2$ [6] are defined by the red and blue bands.

Fig. 3.

Low-definition solutions (1,000-y time bins) for the corrective term $\delta {\zeta }_{esl}\left(t\right)$ for the two lower-mantle viscosity solutions (low-viscosity solution in red with yellow error bars and high-viscosity solution in blue with pale blue error bars).

Fig. 4.

Solution for the ice-volume esl function and change in ice volume. (A) Individual esl estimates (blue) and the objective estimate of the denoised time series (red line). The Inset gives an expanded scale for the last 9,000 y. (B) The same esl estimate and its 95% probability limiting values. Also shown are the major climate events in the interval [the Last Glacial Maximum (LGM), Heinrich events H1 to H3, the Bølling-Allerød warm period (B-A), and the Younger Dryas cold period (Y-D)] as well as the timing of MWP-1A, 1B, and the 8.2 ka BP cooling event. (C) The 95% probability estimates of the esl estimates. (D) Estimates of sea-level rate of change.